The production of 1,4-butanediol from allyl alcohol is a well-known and commercially practiced process. See, for example, U.S. Pat. Nos. 4,238,419, 4,678,857, 4,215,177, 5,290,743 and the like. Generally, the process consists of a hydroformylation reaction followed by hydrogenation step. In hydroformylation, allyl alcohol is reacted with a CO/H2 gas mixture using a rhodium-phosphine catalyst system to form 4-hydroxybutyraldehyde (HBA), with some 3-hydroxy-2-methylpropionaldehyde (HMPA). Then, the HBA is typically separated from the catalyst by water extraction and hydrogenated over a nickel catalyst to form 1,4-butanediol. See U.S. Pat. No. 5,504,261.
The above reaction sequence involves the use of different catalysts and usually different reaction gas mixtures for each of the reactions. For the hydroformylation reaction, most notably a rhodium complex is used together with a phosphine ligand (see, e.g., U.S. Pat. Nos. 4,064,145, 4,238,419, and 4,567,305). Commonly employed phosphine ligands are trisubstituted phosphines such as triphenyl phosphine. U.S. Pat. No. 6,127,584 discloses the use of a trialkyl phosphine ligand having at least 2 methyl groups. The use of diphosphine ligands such as DIOP, trans-1,2-bis(diphenyl-phosphinomethyl)cyclobutane, trans-1,2-bis(bis(3,5-di-n-alkylphenyl)-phosphinomethyl)cyclobutane, and 2,3-o-isopropylidene-2,3-dihydroxy-1,4-bis[bis(3,5-di-n-alkylphenyl)phosphino]butane is also taught in the art, notably in Japan Kokai Nos. 06-279345 and 06-279344 and U.S. Pat. Nos. 4,306,087, 7,271,295, and 7,279,606.
Direct hydrocarbonylation reactions of allyl alcohol to produce 1,4-butanediol have also been taught in the art. It has been reported, for example, in Kokai No. S52-78809 by Kawahito, et al. that 1,4-butanediol can be produced from allyl alcohol in a one-step reaction using a rhodium and a trialkyl phosphine catalyst system. However, these processes typically result in a relatively low ratio of 1,4-butanediol to 2-methyl-1,3-propanediol and also produce a significant amount of less valuable isobutanol by-product. U.S. Pat. No. 6,127,584 discloses a two-step, one catalyst process using rhodium and a trialkyl phosphine wherein higher ratios of 1,4-butanediol to 2-methyl-1,3-propanediol are produced.
In sum, new processes for the direct hydrocarbonylation of allyl alcohol to produce 1,4-butanediol in a single step are needed.